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Increasing sample sizes mean that weighted monthly antibodies estimates for Scotland were published for the first time on 24 November.
Estimate of the proportion of people in Scotland who would have tested positive for COVID-19 antibodies in December 2020
In December 2020, it is estimated that 8.9% of the population in Scotland would have tested positive for COVID-19 antibodies from a blood sample. A 95% confidence interval for this estimate is 7.2% to 10.9 %.
It is estimated that, in December, an average of 398,000 people in Scotland aged 16 and over would have tested positive for COVID-19 antibodies (95% confidence interval: 322,000 to 485,000). These figures are rounded to the nearest 1000. This equates to around 1 in 11 people aged 16 and over (95% confidence interval: 1 in 14 to 1 in 9).
The population used in this analysis relates to the community population aged 16 years and over.
Figure 1: Monthly weighted estimates of the percentage of the population testing positive for COVID-19 antibodies in Scotland, including 95% confidence intervals.
Methodology and further information
The analysis is based on blood test results taken from a randomly selected subsample of individuals aged 16 years and over, which are used to test for antibodies against SARS-CoV-2. This can be used to identify individuals who have had the infection in the past.
It takes between two and three weeks for the body to make enough antibodies to fight the infection but once a person recovers, antibodies remain in the blood at low levels, although these levels can decline over time to the point that tests can no longer detect them. Having antibodies can help to prevent individuals from getting the same infection again.
The presence of antibodies is measured to understand who has had COVID-19 in the past, although the length of time antibodies remain at detectable levels in the blood is not fully known. It is also not yet known how having detectable antibodies, now or at some time in the past, affects the chance of getting COVID-19 again.
These statistics refer to infections reported in the community, by which we mean private households. These figures exclude infections reported in hospitals, care homes and/or other institutional settings.
Weighted estimates are provided with 95% confidence intervals to indicate the level of uncertainty around them. A confidence interval gives an indication of the degree of uncertainty of an estimate, showing the precision of a sample estimate. The 95% confidence intervals are calculated so that if we repeated the study many times, 95% of the time the true unknown value would lie between the lower and upper confidence limits. A wider interval indicates more uncertainty in the estimate.
More information about the COVID-19 Infection Survey in Scotland can be found on the information page on the Scottish Government website, and previous COVID-19 Infection Survey data for Scotland can be found in this collection.